An in-vitro test set-up for evaluation of a voice-producing element under physiologic acoustic conditions

To improve the voice quality of laryngectomised patients, a voice-producing element has been developed. Prior to in vivo testing we constructed and validated an in-vitro test set-up, consisting of a physical model of the subglottal tract and three physical models of the vocal tract, for the vowels /a/, /i/ and /u/ to evaluate the voice-producing element under physiologic acoustic conditions. To meet acoustic conditions described in the literature, we determined the appropriate dimensions of these physical models, using a numerical model of the pressure perturbation in rigid tubes. The numerical model showed that an acoustic equivalent of the subglottal tract could be obtained with a three-tube system and an end impedance. Vocal tract models could be constructed using two- and four-resonator tubes. The physical models were built and successfully validated according to the human acoustic properties. The developed in-vitro set-up can now be applied to test voice-producing elements or vocal fold models under physiologic acoustic conditions.